ritter



NO. 6l|,58|. Patented Sept. 27, I898.

I G. BITTER. TELEPHONE $YSTEM.

[Application filed Feb. 23, 1895.) (No Model.)

4 Sheets-Sheet I.

W :K g 3% R mg a 19H: memos athwn an No. 6ll,58|. Patented Sept. 27, I898.

G. BITTER.

TELEPHONE SYSTEM.

(Application filed Feb. 23, 1895.)

(\No Model.) 4 Sheets-Sheet 2.

THE NORRIS PETERS no Pnorp-unquLyusv-xmmou. n c,

(No Model.)

Patented Sept. 27, I898; e. BITTER.

TELEPHONE SYSTEM.

(Application fi1ed Feb. 23, 1895.)

4 Sheets-Sheet 3.

Patented Sept. 27, I898.

4 ShaetsShee't 4.

(No Model.)

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.ETL

GEORG RITTER, OF STUTTGART, GERMANY.

TELEPHONE SYSTEM.

SPECIFICATION forming part of Letters Patent No. 611,581, dated September 27, 1898.

Application filed February 28,1895. Serial No. 539,521. (No m'odel.) Patented in Germany August 31,1898,No. 78,755; in Sweden August 13,1894, No. 7,820; in France August 18, 1894,1lo. 240,815; in Norway August 20, 1894,1510. 8,972; in England August 29, 18 -1 A'Z3; in Belgium September 5, 1894, No. 111,684; in Hungary October 17, 1894, No.

1,400, and in Austria April 19,1895,No.1,378/45.

T0 at whom it may concern.-

Be it known that I, GEORG RITTER, a citizen of the Empire of Germany, residing at Stuttgart, in the Empire of Germany, have invented certain new and useful Improvements in Telephone Systems, (patented in Germany August 31, 1893, No. 78,755; in Belgium September 5, 1894, No. 111,684; in Great Britain August 29, 1894, No. 16,473; in France August 18, 1894, No. 240,815; in Austria April 19, 1895, No. 1,378/45; in Hungary October 17, 1894, No. 1,400; in Norway August 20, 1894, No. 8,972, and in Sweden August 13, 1894, No. 7,320 and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

My invention relates to improvements in telephone systems. The main object of my invention is to provide a system in which the calling of the central station by a subscriber will be done by merely taking down the telephone from its hook or hanger, thereby avoiding the employment of a magneto or the like and the delay in operating the same.

Another object of my invention is to permit the calling of the central station by means of a battery or other source of electricity located at said central station.

With these principal objects in view and some others which will be obvious to those skilled in the art from the description hereinafter a system embodying my invention, broadly considered, embodies two normally open circuits between the central station and the substations, one of said circuits being open at the substation end and the other at the central-station end, a calling-annunciator at the central station included in the former circuit, a call-bell or its equivalent at the substation and included in the latter circuit, means for energizing the circuits, preferably located at the central station, mechanism at the central station for closing the circuit open at that end, whereby a call is sent from the central station to the substation, mechanism at the substation for closing the circuit open at that end, whereby a call is sent from the substation to the central station, and telephones at the substation and central station which may be switched into one of the circuits. By this construction the telephones at each substation may be so connected that bythe mere act of lifting the telephone from its hook the mechanism for closing the circuit which is employed for calling the central station may be actuated, first, to close the said circuit, then to open the samecircuit, and, finally, to switch the telephone onto the desired circuit which is to be employed for the talking-circuit. At thesame time the normal condition of the system at the substation is such that the circuit open at the centralstation end is kept closed at the substation by said telephone when the latter is hanging on its respective hook and is opened by the removal of the said telephone from the hook.

The invention will be more specifically pointed out hereinafter in connection with the accompanying drawings, in which- Figures 1, 2, 3, and 4 are diagrammatic views of several forms of wiring of a system embodying myinvention, each of which forms will be more particularly referred to hereinafter. Fig. 5 is a detail view of the contactinaking device employed by me in connection with the switch-lever.

In the views the correspondingparts have the same reference letters and numerals, the exponents used with said letters and numerals being varied to indicate in most cases the number of the substation to which the part indicated by its reference letter or numeral belongs.

Referring to Fig. 1,f]" are the usual handtelephones, arranged to be hung on hooks h 7L2, which serve as switch-levers, each being held down by the weight of its telephone when the latter is on its hook and pulled upward when the telephone has been removed by suitable means, such as a spring w 02 When each switch-lever h 72. is up, it comes-into contact with a contact-piece s 8 and when down with a contact-piece rr When the lever is passing from one contact-piece to another,it moves over and forms an electrical communication electromagnetic cut-out y f.

with a contact device a a which is connected to a ground-plate 6 6 At each station is located also a call-bell g At the central station a calling-annunciator k is provided for each substation and also an electromagnetic cut-out 3 1 The wiring of the parts thus far described is as follows: Each substation is connected to the central station by two wires Z Z ,2" 2 the latter being the incoming conductor for each substation and the former the return-conductor. Each incoming conductor 2 e is connected at its respective substation to one pole of the call-bell g 9 the other pole of the said bell being connected to the contact-point r W. The substation end of each return-conductor connects with the corresponding switch-lever 72 71?, preferably at the pivotal point of the same. The telephone f f at each substation is included in a branch circuit formed by the wires a a 1) 01 one end of each branch circuit being connected to its corresponding contact-piece .9 8 while the other end connects with the incoming conductor outside the call-bell g 9 The central-station end of each return-conductor includes the coils of its respective calling-annunciator 70 k and is controlled outside the said annunciator by the switch-lever of its The extreme inner end of each return-wire is connected to the appropriate bus-bar of a main battery, which, for a purpose hereinafter mentioned, is subdivided into parts to 10 one end of the entire battery being connected to a bus-bar b, the opposite end being connected with the ground e, while a point intermediate the subdivisions of the battery is connected with a second bus-bar 12 The reason for this subdivision is as follows: When a substation is so far removed from the central station that a considerable amount of battery-power is required to ring over the said substation circuit the entire battery is to be employed, and when a substation is near enough to the central station to require but a small amount of battery-power for ringing then one of the subdivisions of the said battery may be employed. Hence all those substations requiring full battery-power have the central-station ends of their respective return-conductors Z connected to the bus-bar l), and those substations requiring only a single subdivision of the battery have the similar ends of their return-conductors b united to the bus-bar 5 This subdivision can be carried to a further extent, if necessary, another bus-bar being added for each additional subdivision of the said battery.

The central switchboard apparatus is constructed as follows: Each return-conductor Z? is provided at the switchboard with the usual jack-springs 7' and each incoming conductor 2 2 is provided also with jacksprings m m In addition to these jacksprings a third set of jack-springs n n are connected by wires 1119 with their respective bus-bars b b according to the amount of battery-power required for operating their respective substation-circuits.

All the sockets 0 0 for each substation are in electrical communication with each other and connected by a suitable conductor, as c 0 to'one pole of the corresponding electromagnetic switch g the other poles of said switches being connected to one pole of a local battery d, which I will call the cut-out battery. The other pole of the saidcut-out battery d is connected to the plug-connectors, which will now be described. Each pair of plug-connectors comprises two kinds of plugs and their connections,one plug,T, being what I will term the answer-plug" and the other,

If, the calling-plug.

The answer-plug is arranged to enter any of the sockets only far enough to engage the jack-springs 3' and m the third jack-spring n being too short for engagement with the said plug. On each answer-plug there are two contact rings or plates 1 2 and also a contact-collar or similar device 3. The plate 1 is arranged to come into contact with the jackspring m while the plate 2 is arranged to contact with jack-spring 7' The collar 3 is so placed that when the answer-plug is properly placed in any socket it will contact with the said socket.

The calling-plug t is provided with a plate 4, arranged to engage the j ack-sprin gm when the plug is partly inserted into a socket and also to engage the jack-spring at when the plug is pushed into said socket to its full eX- tent, whereby electrical communication will be established between the jack-springs m and n through the said plate 4. The callingplug 25 is also provided with two plates 5 and (i, the former of which engages the jack-spring j when the plug is only partly inserted into the socket and the latter plate 6 engaging the same jack-spring] when the plug is pushed fullyinto the said socket. Moreover, the said calling-p111 g is also provided with a long contact-collar 7 or similar. device for forming an electrical connection with the socket, both when the plug If is only partly in the said socket and when it is fully pushed into the same. spring 8, whereby the plug may be inserted into a socket and fully pushed into the same by the operator, but will be retracted by the action of the spring 8 as soon as released by the operator.

The plugs are connected by flexible connections as follows: plate 2 with plate 5 by conductor U, and plate 1 with plate 4 by conductor V. In addition each collar 3 and 8 is connected by a flexible conductor N with the common conductor X, leading from the local cut-out battery d. Furthermore, plate 6 of the calling-plug is connected by a flexible connection Y with a conductor q, leading to the grounded end of the main battery w 10 Moreover, a bridge-circuit Z is formed between the wires U and V, in which circuit is in- The calling-plug is provided with a cluded an annunciator 12, which I shall term the clearing-out annunciator and which 1 shows a signal by the dropping of its armature when its electromagnet is demagnetized. In the said branch circuit Z is also included a local clearing-ont-annunciator battery 11 and a telephone 9, which serves as the central-station or operators telephone and which can be cut out of or into any desired plugconnector circuit by means of a suitable switch device which when thrown to cut out the telephone closes the bridge-circuit around the telephone. In the drawings I have shown merely a conventional cutout switch for this purpose; but it is to be understood that in ordinary practice where a large number of plug-connectors are in use some of the usual forms of multiple switches must be used for making the connections between the operators telephone on the local bridge-circuit Z and the desired plug connection and for closing the bridge-circuit outside the telephone.

The operation of the system thus far described is as follows: In the normal condition of the systemthat is, when the substation instruments are out of use-the substationtelephones if f are hanging on their respective hooks and the switch-levers 77/71 are in contact with the contact-pieces r 0*,

whereby the conductors Z and 2 Z and are respectively in circuit with each other. The plugs T are removed from the sockets and i the cut-out switches y 1/ closedby their springs, the calling-annunciators therefore being included in the open circuitwith said wires Z e Z .2 respectively. These open circuits are each connected to one pole of the main battery through the bus-bars b. 12 the only reason for not connecting all substation return-wires Z Z &c., with one bus-bar having been previously explained. It will be assumed now that the subscriber at substation II desires to communicate with the central and then with the subscriber at substation I. To do this, he removes his telephone f3 from the hook on the switch-lever k whereby the latter is free to be drawn upward by its spring, and in thus moving upward comesinto contact laterally with and moves over the contact device a which closes thecircuit and causes the dropping of the signal-disk by the respective calling-annunciator k The path of the circuit is as follows: from one pole of the main battery to 10 along the bus-bar Z), out over conductor Z passing through the coils of the calling-annunciator k and across the closed switch of 3 to the switch-lever h at the substation II,thence through the contact device a to the ground at c and back through the earth to the ground-plate e, from whence it passes to the opposite pole of the battery w 10 The current in passing over this circuit causes the dropping of the target or disk of the calling-annunciator k in the usual way, which notifies the operator of the number of the station which has sent in a call. The operator then pushes the answer-plug. T into the proper socket of the line over which the call has come (in this case into a socket 0 and switches the central-station telephone onto the bridge-circuit, which connects with the plug-connector then in use. The switch-lever 71 from which the telephone f was removed, after passing the contact device a is brought against the upper contact-piece 5 so that as soon as the operator has made the connections above mentioned a talking-circuit is established, which will be more particularly described hereinafter. At the same time by the insertion of the answer-plug T the local circuit of the electromagnetic cut-out is closed, this circuit being as follows: from local battery cZ, over the wire X, to the plug-connector wire W, thence to the contact-collar 3 of the plug T, through the socket 0 by way of the wire 0 through the coils of the electromagnetic cut-out 3 and thence to the other pole of said local battery cZ. this local circuit causes the breaking of the line Z from its calling-annunciator. Thetalking-circuit is as follows: from the local clearing-out-annunciator battery 11, across switch 10, over the central telephone 9, to the plugconnector wire U, thence to plate 2, out through jack-spring j to conductor Z over the same to the pivotal point of the switchlever 7L2, thence to contact-point 8 over the substation branch, through the telephone f to the conductor 2 and back to the central station, thence through jack-spring m to plate 1, along the plug-connector wire V to the other end of the local bridge circuit, and thence back to the battery 11, passing through the coils of the stop-annunciator 12, whose armature is thereby attracted. The operator having obtained the number of the substation with which the subscriber at substation II desires to communicate (which, it is assumed, is station I) then makes the connection as follows; plug Z is inserted in the desired substation-socket 0 and pressed inward to its fullest extent, whereby the circuit of the local cut-out battery is closed, and then the calling-circuit over the wires to substation I is established. Theformer circuit is as follows: from battery (Z, over wires X and V, to the contact-collar 7, thence through the socket o by wire 0 to the electromagnetic cut-out 3 around the coils of the same back to the local battery cZ, whereby a break is made. in the wire Z outside its calling-annunciator The calling-circuit to substation I is as follows: from the battery 10 through the appropriate bus-bar (flout over the wire 13 to jack-spring n, thence by way of plate ton the calling-plug tto jack-spring m, thence to conductor .2, over the same to the call-bell g of the desired substation,thence to the contact-point r, through the switch-lever h, back over conductor Z to the jack-springj, thence to plate 6, through wire Y of the plug-connector to wire q, and back to the other pole of. the battery. The completion of this circuit causes the ringing of the subscribers call-bell. As soon as the The completion of operator has made the call by the insertion of the calling-plug t, as described, the pressure of the finger is released from the end of said plug, and the latter is then partly retracted from the socket by its spring 8 and the contact-plate 5 brought into contact with the jack-spring j, while the contact-plate 4 is removed from contact with the jack-spring u, but still remains in contact with the jackspring m. This partial retraction of the calling-plug, together with the removal of the telephone f from its hook by the subscriber called, establishes a talking-circuit between the two connected substations with the operators instrument in a bridge between the two stations, or, in other words, the two substations are in parallel arc from the clearingout annunciator and battery. The complete talking-circuit between the two substations may then be considered as a duplication of the talking-circuit between the central station and the calling substation II, previously described, it being understood that the current set up by the vibration of each substationtelephone divides when it reaches the bridge circuit Z, a part going over the said bridgecircuit, and thereby acting on the telephone of the central station, while the remainder goes on to the other substation. During the existence of the connections for talking, as above pointed out the clearing-out annunciator 12 has its electromagnet energized, and thereby attracts and holds its armature with the attached disk. As soon as both subscribers on the connected lines have finished and hung up their respective telephones the circuit through the clearing-out annunciator 12 is broken, owing to the fact that the substation-telephones when hung upon their respective hooks pull the switch-levers h 72 downward out of engagement with the upper contact-pieces s s and into engagement with the contact-pieces r W. The armature of the clearing-out annunciator then'falls, and the operator is informed that the lines connected by the plug-connector are out of use. The said operator then removes the plugs T tfrom the sockets 0 0 and in doing so breaks the local cut-out circuits, thereby causing the electromagnetic cut-outs 3 g to release their armatures, which, being drawn back by their respective springs, close the breaks in the lines Z Z and thus establish the connections again between the said lines Z Z and their respective calling-annunciators 70 thus restoring the lines to their normal condition.

In Fig. 2 I have shown a form of wiring in which the substations are arranged in groups, two substations being shown in each group in this instance, though it is to be understood that as many substations may be included in a group as are desirable. Each group has a common incoming conductor a z, the said conductor being connected up to the corresponding jack-springs of the group to which it belongs. For instance, conductor a is connected to the jack-springs m m while conductor a is connected to the jack-springs m m In this form of Wiring a slight difference in the connections at the central station is necessary, and for this reason I will now specifically describe those parts. Answer-plu g T,which in the construction shown in Fig. 1 was not provided with a spring to partly retract it, in the form now under consideration is provided with such a spring 14 in the same manner as the calling-plug t in Fig. 1, whereby the answer-plug T will be partly retracted by its spring 14 when the pressure of the operators finger is removed. Moreover, this answer-plug T has an additional contact-plate 13 for a purpose hereinafter mentioned. When the said plug T is inserted in a socket and pressed inward to its full extent, its plate 13 comes into contact with the jack-spring m m &'c., while when said pressure is removed the plug is partly retracted by its spring 14 and rests with its plate 1 in contact with the said jack-spring. Instead of the plate 1 of the plug T being connected with the plate 4 of the plug t, as in the construction shown in Fig. 1, it is connected with the plate 5'01. said plug t by the conductor V of the plug-connector. The plate 2 therefore is in this case connected to plate 4 by the conductor U which does not extend directly from one plate to the other, but has a gap in it which is closed by the clearing-outannunciator local circuit, this circuit being the same as heretofore described in connection with Fig. 1 and includes the same apparatus. Abranch wire Z leads from that part of conductor U which connects with plate 4 to the plate 13, carried by the answer-plug T. In other respects the connections are as in Fig. 1. The normal condition of the circuits and the path of the current in calling the central station are the same as in the construction first described. It will be assumed now that substation I has called the central station. The operator inserts the answerplug T in the appropriate socket 0, forcing said plug inward to its full extent, thereby ICC IIC

compressing its spring 14 and bringing the contact-plate 13 into electrical communication with the jack-spring m, at the same time closing the local cut -out circuit and causing the electromagnetic switch y to open the line Z. The talking-circuit between the central station and substation I is as follows: from the central telephone 9 to the wire Z, thence to plate 13, out through jack-spring m to conductor 2, thence by wire 2' to its connection with the telephone branch circuit, over said branch circuit through telephone f to the contact-point s, thence through the switchlever h to wire Z, along the latter to the jackspring j, thence to the plate 2, and from there by wire U to the clearing-out-annunciator circuit, around which it passes to the startingpoint. The operator, having received the number of the station with which the subscriber at substation I desires to converse, (and which it will be assumed is substation 3,)

then inserts the calling-plug t in the socket o pushing said plug inward to its full extent. The calling-circuit in this case is substantially the same as that described in connection with Fig. 1. As soon as pressure is removed from the plug t the latter ispartly retracted, and consequently when the subscriber at substation 3 takes down his telephone the through talkingcircuit is completed. This circuit is as follows: from telephone f to contactpoint 5, over switch-lever h to wire Z, along the same to jack-spring], thence to plate 2, then over the two parts of conductor U and the local circuit Z to the plate 4,thence through jack-spring m to the conductor 2 over the same to the wire 2 thence to the telephone branch circuit of substation 3,0ver said branch circuit, through the telephone f to the contact-piece 5 then by way of the switch-lever 7L3 to wire Z over the same to jack-spring 7' from there by way of plate 5, conductor V,

plate 1, and jack-spring m to conductor 2, and then by way of -the latter back to the branch circuit at substation I. In this modification of my invention the clearing-out annunciator will fall as soon as either telephone of the connected substations has been replaced on its hook.

When a substation of one group is connected with the corresponding substation of the same group-as, for instance, substation I with substation IIthe connections are made in exactly the same manner as just described, but the talking-circuit will not be exactly the same, since in such a case the incoming wire 2 is common to both connected substations. Therefore under these conditions it will be obvious that the substation-line Z, with its instruments and with the clearingout-annunciator circuit and instruments, is in parallel with that part of the conductor z from the jack-spring m to the point of connection with the substation-wire 2.

Instead of arranging the substations in groups, each group'having an individual'incoming wire a z, 860., it is obvious that I may use a single incoming conductor 2 for all the substations. This form of my invention is shown in Fig. 3. The central-station apparatus is similar to that shown in Fig. 2; but the connections through the plug-eonnector are like those shown in Fig. 1-that is to say, the contact-plates 2 and 5 are connected by the wire U, the plates 1 and 4: by the wire V, while the clearing-out-annunciator circuit forms a bridge between the said wires U and V. The mode of operation will be fully understood from the drawings when considered in connection with the descriptions given with regard to Figs. 1 and 2.

In Fig. 4: I have shown a form of wiring embodying my invention wherein the incoming wires are connected with each other by a cross-line Z Z just outside the call-bells. Moreover, at the central station there are no electromagnetic cut-outs in the conductors l Z &c. The breaking of said lines is done in the following manner: Opposite each socket 0 o 0 &c., the said lines have each a gap or break which is normally bridged by two jacksprings j J'j J 656.,11116 jack-springs of each pair normally staying in contact with each other. Upon the insertion of a plug in a socket the corresponding jack-spring of the series j ff, dad, will be pushed away from the corresponding jack-spring of the other series J J 2 J ac. and thereby the respective line Z Z &c., will be opened. The plug-connectors in this construction do not contain as many conductors, the contact-collars 3 and 8 of the two plugs being omitted, together with the connecting-wire W and all of the local cut out circuits and apparatus. Furthermore, the contact-plates 1 and 4. are omitted from the two plugs T t and also the connector-wire V, it being understood, of course, that no jack-springs of the series m m 850., or of the series W11 c. are employed,owin g to the fact that the incoming wires .2 5 &c., do not extend from the central station. Moreover, in this system the clearing-out-anniinciator circuit and instruments, including the central-station telephone, form a part of the plug-connector conduotor'U instead of forming a bridge-circuit, as they do in Fig. 1. In this modification of my improved system the removal of one of the substation-telephones from its hook causes the closing of the calling-oircuit through the earth by means of the switch-lever coming into contact with its respective contact device a a the, exactly in the same manner as described in connection with the form of system shown in Fig. 1. Upon receiving the call the operator places the answer-plug in any desired socket of the calling-line and must also insert the other plug of the same connector in a socket of the line from either substation adjacent to the one which has called. For instance, let it be assumed that substation I has called. Thenthe operator puts the answer-plug T in one of the sockets 0 and the calling-plug tin one of the sockets-say, for example, 0 In this way a talking-circuit is formed from substation I as follows: from telephone f to wire 2, thence over wire Z to wire 2 thence through the coils of the call-bell g to the contact-point r thence through the switch-lever h to line Z over said line to the j ack-springj from which it enters the contact-plate 5,passes through the connector-wire U, operators telephone 9, clearing-out-annunciator battery 11 annunciator 12, to contact-plate 2 on the plug T, thence through j ack-spring j, over line Z, to switch-lever h, and thence by way of the contact-point s and thebranoh circuit to the telephone f. The operatorcan now converse with the subscriber at substation I and inquire the number of the station which it is desired to call. It will be assumed that the substation is No. IV. The calling-plug tis now withdrawn from the socket o and in serted to itstull limit in one of the sockets 0 of the desired line, whereby the contact-plate 6 is brought into contact with the jack-spring j, and the current then flows from the battery 10 through bus-bar b to the wire Z around the coils of the calling-annunciator I0 and out to substation V, where it passes through the switch-lever h to contact-point r thence around the coils of the call-bell g and outward over wire Z5 to the wire Z along the latter wire to wire a thence inward over said wire .2, around the coils of the call-bell 9 to the contact-point r, then over the switch-lever h to wire Z", back to the jackspring jflthence through contact-plate 6,wires Y and q, to the main battery. Attention is called to the fact that the current flowing through the coils of the call-bell q passes in a direction opposite to that which it takes in going through the coils of the call-bell 9. Hence, as the latter bell is the one to be rung, while the former is not to be operated, all the call-bells under this form of wirin g are so arranged as to be rung only by a current passing inward or toward the switclrlever. This may be done in any suitable way, as by using polarized magnets for the bells. As soon as the operator has caused the ringing of the bell at substation IV the pressure on the plug t is released and the latter is partly retracted by its spring 8 in a manner heretofore described, thus bringing the contact -plate 5 into contact with the jack-springj and thereby establishing the completed talking-circuit between substations I and IV, it being presumed that by this time the subscriber at the latter station has taken down his telephone. The plug-connector wire U will complete the circuit from j to 9' while the bus-wire I), battery-w, bus-bar I), and the wires Z Z, r and Z will complete the circuit from the station I to the station IV in an obvious manner. It will be seen that the central-station telephone is in the completed talking-circuit, as also the clearing-out annunciator 12. The operator can listen to the conversation, as desired, or can by means of switch 10 cut out the said central-station telephone. The falling of the clearing-out-annunciator' disk will ensue upon the breaking of the circuit by the hanging up of either telephone, whereupon the plugs are to be withdrawn and the circuits thus restored to their normal condition. WVhile I have in the system just described shown a mechanical means for opening the lines Z Z 850., instead of the electromagnetic cut-outs shown in Fig. 1, it is clear that I may employ the latter, if desired, with the said last-described system instead of the jacksprings J &c.

In Fig. 5 I have shown a detail of one form of contact device which in connect-ion with the switch-lever h 7?, &c., serves to make and break the various circuits at the substation. It will be understood that as the switch-lever h is moved upward by its spring upon the removal of its telephone it comes into contact with its respective contact device a, &c. and

- as shown.

then passes out of contact with its said contact device. While in such contact, as has been previously explained, it closes a circuit to the central station and throws the callingannunciator at said central station. It will be clear that if the switch -lever contacted with said contact device 011 its downward movement at the close of a conversation and upon the replacement of the telephone on its hook it would again close the circuit which includes the calling-annunciator and would thereby cause the target of the latter to drop. To avoid this dropping of the annunciatortarget on the downward movement of the switch-lever is the purpose of the construction shown in said Fig. 5. The switch-lever h, instead of coming directly into contact with its contact device, is provided atits rear end with a contact-spring hiwhich is secured to said switch-lever h with a pair of screws, The contact device a is in this case placed at the rear of the pivotal point of the switch-lever and is cam-shapedthat is to say, it forms an inclined plane up which the contact-sprin g 71. can ride when the switchlever is moving upward. The outer surface with which the spring contacts is of conducting material, whereas the rest of the device a is not, and hence on the downward movement of the switch-lever the contact-spring 71 is brought into contact with the under face of the contact device a, which, as before stated, is made of insulating material, and therefore prevents the circuit from being closed.

From the description given thus far it will be seen that each form of wiring disclosed embodies the essential features of my invention asset out at the beginning of this specification. For instance, referring only to substation I in Fig. 1, the circuit normally open at the substation end is that in which the telephone switch-lever h and the plate a are included,while the circuit normally open at the central-station end'is that including the signal-bell g, the telephone switch-lever h when down, and the two jack-springs j and m, which are normally out of contact with each other. It will be noted that when the centralstation operator inserts a plug into a jack in order to call the substation connected with said jack the connection between the battery and the principal wire leading to said substation is reversed. This is shown, for example, in Fig. 1, where the battery w 10 normally has one end connected to the principal line-wire Z this connection being severed upon the insertion of the plug 25 into the socket O, owing to the operation of the electromag net-switch y,while the plug-connector 25 makes a connection over the wires Y and q with the opposite pole of the battery w w By this means for reversing the battery connection with the principal line conductor the circuit over the subordinate line conductor is closed, as will be understood from the description of the operation hereinbefore given, and the call'bell at the desired substation will be rung.

It will be seen that from the central station to each substation are run two line conductors, one of which is connected to one pole of a battery whose other end is grounded. One line-Wire is also in permanent electrical con nection with the telephone switch-lever, preferably by being connected to the pivotal point of the said switch-lever. The other line conductor contains the calling-annunciator at the central station. In order to distinguish these line conductors in the claims, I will call the former the principal line conductor and the latter the subordinate line conductor, though it is to be understood that these terms are used in an arbitrary sense merely for the purpose of identification.

Having thus fully described my invention, what I claim as new, and desire to secure by Letters Patent, is-

1. In a telephone system, the combination, with principal and subordinate line conductors, a call-bell in the subordinate line conductor, a branch circuit around the call-bell and having one end connected to the subordinate conductor, a contact device connected to the ground, and a switch-lever arranged when in one position to connect the line conductors through the call-bell, when in its other position to connect said line conductors through the branch circuit, and when moving from one of said positions to the other to connect the principal line conductor with the ground through said contact device, of telephone apparatus in the branch circuit, a battery at the central station having one pole connected to the ground and the other pole connected to the principal line conductor, and an annunciator in said principal line conductor at said central station, substantially as set forth. 4

2. In a telephone system, the combination, with principal and subordinate line conductors, a call-bell in the subordinate line conductor, a branch circuit around said call-bell and having one end connected to the subordinate line conductor, a contact device connected to the ground, a switch-lever arranged when in one position, to connect the line conductors through the call-bell; when in its other position to connect said line conductors through the branch circuit, and, when moving from one position to the other, to connect the principal line conductor with the ground through said contact device, a telephone apparatus in the branch circuit, a battery at the central station having one pole grounded and the other pole connected to the principal line conductor, and an annunciator in said principal line conductor, of means-at said central station for reversing the battery connection with the principal line condu ctor and closing the circuit over the subordinate line conductor, whereby the substation is called.

3. In a telephone system, the combination,

with principal and subordinate line conductors, a call-bell in the subordinate line conductor, a branch circuit around said call-bell and having one end connected to the subordinate line conductor, a contact device connected to the ground, a switch-lever arranged when in one position, to connect the line conductors through the call-bell; when in its other posi tion to connect said line conductors through the branch circuit, and, when moving from one position to the other, to connect the principal line conductor with the ground through said contact device, a telephone apparatus in the branch circuit, a battery at the central station having one pole grounded and the other pole connected to the principal line conductor, and an annunciator in said principal line conductor, of means at the central station for cutting out the annunciator, reversing the battery connection with the principal line conductor and closing the circuit over the subordinate line conductor.

4. In a telephone system having a plurality of substations, the combination, with principal and subordinate line conductors between the central station and each substation, a callbell in each subordinate line conductor at its respective substatioma branch circuit at each substation around its call-bell and having one end connected to its subordinate line conductor, a contact device at each substation connected to the ground, a switch-lever at each substation arranged when in one position to connect its respective principal and subordinate line conductors through the call-bell; when in its other position, to connect said line conductors through the respective branch circuits, and when moving from one position to the other to ground its principal line conductor through the contact device, telephone apparatus in each branch circuit, annunciators at the central station, each annunciator being connected to its respective principal line conductor and a battery at the central station, having one end grounded and its other end connected to all the principal line conductors, of means at the central station for connecting the line conductors from one substation with the corresponding line conductors from any other substation, and simultaneously cutting out the battery and the respective annunciator, whereby the substations are putin telephonic communication with each other.

-5. In a telephone system having a plurality of substations, the combination, with principal and subordinate line conductors between the central station and each substation, a callbell in each subordinate line conductor at its respective substation, abranch circuit at each substation around its call-bell and having one end connected to its subordinate line conductor, a contact device at each substation connected to the ground, a switch-lever at each substation arranged when in one position to connect its respective principal and subordinate line conductors through the call-bell; when in its other positionto connect said line IIO from any other substation,- and simultaneously cutting out the battery and the respective annunciators, a telephone apparatus at the central station, and means for including said telephone in the circuit formed by the connected substation line conductors.

In Witness whereof I have hereunto signed my name in the presence of two subscribing Witnesses.

GEORG BITTER.

Witnesses:

WILHELM LEVY, CARL HUBER. 

